Among mammals, modern cetaceans (whales, dolphins, and porpoises) are unusual in the absence of hind limbs. However, cetacean embryos do initiate hind-limb bud development. In dolphins, the bud arrests and degenerates around the fifth gestational week. Initial limb outgrowth in amniotes is maintained by two signaling centers, the apical ectodermal ridge (AER) and the zone of polarizing activity...

In the legless lizard, Ophisaurus apodus, the hind-limb primordium appears on the caudal extremity of the Wolffian ridge at an early stage in the development of the embryo (4-2 mm long). Three somites each send an extension into this young bud and distribute cells in its mesenchymal mass of cells. An apical epiblastic ridge, appearing as a fold from the exterior, forms on the limb-bud, which at...

developing supernumerary limbs is a rare congenital condition that only a few cases have been documented. depending on the cause and developmental conditions, they may be single, multiple or complicated, and occur as a syndrome or associated with other anomalies. polymelia is defined as the presence of extra limb(s) which have been reported in human, mouse, chicken, calf and lamb. it seems that...

Nanomaterials are particles with 10 to100 nanometer size. They can easily be transportedthrough the skin, lung alveoli, and placenta. Materials in nano scales show different propertiescompared with the same materials in macro or larger scale. It is found that zinc element is anessential metal for normal physiological functions. However increase or decrease of this elementduring pregnancy, for e...

Recent studies have indicated that ATRA inhibits chondrogenesis and can lead to congenital clubfoot (CCF). The molecular mechanism of ATRA-induced chondrogenesis is not clear. As RhoA/ROCK and SDF-1/CXCR4 signaling play important molecular roles for a variety of cellular processes, we hypothesized that RhoA/ROCK2 and SDF-1/CXCR4 signaling are involved in ATRA-induced chondrogenesis in rat embry...

Conservation within intergenic DNA often highlights regulatory elements that control gene expression from a long range. How conservation within a single element relates to regulatory information and how internal composition relates to function is unknown. Here, we examine the structural features of the highly conserved ZRS (also called MFCS1) cis-regulator responsible for the spatiotemporal con...

The vertebrate Hox genes have been shown to be important for patterning the primary and secondary axes of the developing vertebrate embryo. The function of these genes along the primary axis of the embryo has been generally interpreted in the context of positional specification and homeotic transformation of axial structures. The way in which these genes are expressed and function during the de...

Although the vertebrate limb bud has been studied for decades as a model system for spatial pattern formation and cell specification, the cellular basis of its distally oriented elongation has been a relatively neglected topic by comparison. The conventional view is that a gradient of isotropic proliferation exists along the limb, with high proliferation rates at the distal tip and lower rates ...

purpose: microgravity causes major changes in various systems of the body in space, such as shift in cerebrospinal fluid, decreased red blood cells count, and electrolyte loss. these complications are very important in space and we should find new approaches to prevent the side effects of microgravity in astronauts. materials and methods: this experimental study was conducted on 21 adult male r...

Purpose: Microgravity causes major changes in various systems of the body in space, such as shift in cerebrospinal fluid, decreased red blood cells count, and electrolyte loss. These complications are very important in space and we should find new approaches to prevent the side effects of microgravity in astronauts. Materials and Methods: This experimental study was conducted on 21 adult ma...